The present invention relates to electronic musical instruments for electrically generating tones by driving various circuits, devices, etc. with electric power supplied from a power supply, and more particularly to electronic musical instruments which drive various circuits, devices, etc. by a battery.
Recently, electronic musical instruments, which are arranged to electrically generate tones while simulating performance styles of natural musical instruments (i.e., so-called “acoustic musical instruments”), such as a piano, organ, trumpet and guitar, have been widely used in place of the natural musical instruments. In these electronic musical instruments, an electric power supply is required for supplying electric power (voltage/current) to various electrically-operable circuits, devices, etc., such as a tone generator circuit, amplifier, speaker and other electronic devices, to drive these various circuits, devices, etc. Particularly, there have been known portable, small-sized and lightweight electronic musical instruments which can use a battery as the power supply. Manganese-type dry batteries are normally used in the conventionally-known portable, small-sized and lightweight electronic musical instruments. In recent years, however, it has become possible to use (re)chargeable storage batteries (secondary batteries), such as nickel-cadmium, nickel-hydrogen and lithium ion batteries. One example of such an electronic musical instrument is disclosed in Japanese Patent Application Laid-open Publication No. 2002-207480.
As noted above, some conventionally-known electronic musical instruments can use a dry battery or chargeable storage battery (secondary battery) as the power supply for driving various circuits, devices, etc. of the electronic musical instrument. However, in the case where a dry battery is used, the capacity of the dry battery is insufficient to drive the electronic musical instrument for a long time, and thus, the user has to prepare in advance many dry batteries and frequently change the dry batteries, which tends to be very cumbersome. In the case where a storage battery (secondary battery) is used, on the other hand, there can be achieved the advantage that the storage battery is greater in capacity than the dry battery and can thereby drive the electronic musical instrument for a longer time. However, because the storage battery requires a separate charging power supply (e.g., power supply of 100 V) and the charging requires a considerable time, it is not possible to readily charge and reuse the storage battery outdoors where such a charging power supply can not be readily secured. Therefore, in the case where the storage battery is used, the electronic musical instrument can be used only in limited places, which would result in poor user-friendliness and usability of the electronic musical instrument.